Air-compressor.



F. B. HOLDSWORTH.

AIR COMPRESSOR.

'l APFLlcMmN FILED mms. 1912. j M bmg, 312m, mmm Nw, 2f, 19111 3 SHEETS-SHEET 2.

F. D. HOLDSVVORTH.

AIR COMPRESSOR.

'APPucATluN FILED MAY a. |912.

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3 SHEETS-SHEET Ywith the inlet-opening wide open.

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FRED D. HOLDSWORTH, OF CLAREMONT, NEVI HAMPSHIRE, ASSIGNOB., BY MESNE ASSIGNMENTS, TO SULLIVAN MACHINERY COMPANY, OF BOSTON, MASSACI-IU- SETTS, A CORPORATION OF MASSACHUSETTS.

AIR-COMPRESSOR.

maaien.

Specification of Letters Patent.

Application led May 8, 1912. Serial No. 695,875.

To all whom t may concern.'

`'Be it known that I, FRED D. I-IoLDswoRrH, a citizen of the United States, and a resident of Claremont, county of Sullivan, and State of New Hampshire, have invented an Improvement in Air-Compressors, of which the following description, in connection with the accompanying drawings, is a specification, like characters on the drawings representing like parts.

, his invention relates to elastic fluid compressors, and more particularly to compressors of the multi-stage type.

In the operation of air compressors which are driven byan external source of power whichl runs at a constant speed, such as electric motors, gas or gasolene engines, in order to maintain a constant air pressure, it is necessary to interrupt the flow of air through the machine when the pressure in the receiver reaches the desired point, and reestablish the flow as soon as the pressure in the receiver has fallen a few pounds. This is usually accomplished by placing a balanced valve, commonly called an unloading valve, on the main inlet supply to the compressor and attaching to this valve a suitable piston, which moves the valve to its open or closed position by means of a small regulator which is piped to the main air receiver. When this unloading valve is closed by the rise in the receiver pressure, the compressor rapidly forms a more or less complete vacuum in all of its internal air passages. Owing to the construction of this form of unloading valve, it is impossible to make it absolutely air-tight when it is closed, so that a small quantity of air Hows through the machine, which air has to be compressed and delivered to the main receiver. Instead of compressing this air from ordinary atmospheric pressure, however, it may be compressed from only one or two pounds absolute pressure up to receiver pressure. This greatly increases the ratio of compression, and 'as the heat generated in compression is directly dependent upon the numberv of times the air is compressed, it will readily be seen that when the air reaches its final pressure in the aircylinder, it will be heated, very much in excess of the temperature obtained in compression under normal running conditions This high temperature is detrimental to the oil used for lubrication, and is a source of dan- 4 ger, inasmuch as the extreme heat may ignite the oil, or if the oil is diffused through the air in proper proportions, an explosion may result. This is especially true of multi-stage compressors where the pressure is carried to several hundred pounds per square inch. This invention is more particularly concerned with the provision of an auxiliary unloading valve which may be employed in connection with the second or high-pressure` cylinder of a two-stage compressor, or with the second and third cylinders of a three-stage compressor, or to the succeeding cylinders of a compressor of any desired number of stages.

In my co-pending application Serial No. 695,87 6, of even date herewith, I have disclosed an elastic fluid compressor similar in its general characteristics to my present invention but specifically dierent. therefrom, and in that application I have claimed my invention broadly in such a manner as to dominate the present application.

My invention will be best understood by reference to the following description, when taken in connection with the accompanying illustration of one specific embodiment thereof while its scope will be more particularly pointed out in the appended claims.

In the drawings:

Figure l is a central longitudinal vertical section partly` in elevation of a compressor embodying my invention; f

Fig. 2 isa cross-sectional view of the compressor on line 2 2 of Fig. l; A

Fig. 3 is a longitudinal vertical section at an enlarged scale of one end of the highpressure cylinder, which in the present embodiment; is of the double-acting type, the

front end being precisely similar in construction. This view shows the position of the auxiliary unloading valve under normal running conditions; and

Fig. 4 is a sectional view partly in elevation similar to Fig. 3, showing the auxiliary unloading valve in its open position, as it appears when the main unloading valve closes.

Referring tothe drawings and to the em-` Patented Nov. 27, im?.

'usual construction,

bodiment ofv my invention which I have there disclosed, for illustrative purposes, I

yhavethere shown a multi-stage compressor,`

herein having two cylinders, a low-pressure cylinder and a high-pressure cylinder 6, the former drawing its supply from an inlet pipe 7 into an inlet chamber 8, and delivering the compressed air into an outlet chamber 9, connected by'a pipe 10 to an intermediate receiver 11, which as is usual cools the air before it passes to the highpressure cylinder. This receiver', which is commonlycalled an inter-cooler, deliversy the air into an inlet chamber 12 of the highpressure cylinder G, whence itpasses to an outlet chamber 13, as will appear hereinafter.v VThis outlet chamber in practice is connected to a main receiver which I have not shown herein assit is unnecessary to the. illustration of my present invention. The main inlet 7may be controlled as is usual by means of a main unloading valve 1% of the balanced type. This valve is usually controlled by a suitable piston which moves the valve to its open or closed position by means of a. small regulator which is piped to the' main air receiver, these parts beine` of usual and well-known construction, and a further description of them being unnecessary to an understanding of my present invention.

`The auxiliary unloading valve which forms the subject matter or' my present invention may be applied to any cylinder of aV multi-stage compressor beyond the first, or low-pressure cylinder,-that is to say, it

may be applied to thesecond or high-pres-V sure cylinder of a two-stage compressor, or to the second and third cylinders of a. threestage compressor, but for the present purposes, it will be convenient to describethe same in connection with the second or highpressure cylinder of a two-stage compressor.

VReferring now to Figs. 8 and si, I have there shown one end of the high-pressure cylinder 6, herein or the double-acting type, the other end b cing precisely similar in construction. This cylinder is provided with a head 15,- in which is located an inlet valve 16,- which maybe of any usual or desired construction, the same being herein of the oscillating type, being given an oscillating motion at the proper intervals in the operation oi the machine by suitable mechanism connected with the crank-shaft. (See Fig. '1); The cylinder is also provided as usual with a discharge valve 17, which may be of any with" 'av spring 1S tending to seat the same and operating as usual. to open and permit the air lcompressed in the cylinder to flow into'th'eoutletchamber'1S, and thence to the usual main air receiver. )Within 'the cylinder' is av usual piston 19, which when moved toward the right (Fig. 3) draws the air'through the "inlet chamber 12 and its herein being provided' connections with the low-presure cylinder 5, and upon the closingy of the inlet valve 16, as shown in Fig. l, the piston moves toward the left, thereby compressing the same in the usual manner; and Vwhen the pressure in the cylinder is equal to yor slightly greater than the pressure in the discharge chamber 13, the discharge valve 17 will lift from its seat and allow the air to beforcedout of the cylinder. To prevent the formation or' a more or less complete vacuum when the unloading valvel on the main inlet 7 closes, I have provideda valve 20 which'is adapted to open or close a port-21 leading from the interiorfof thecylinder 6 to the inlet chamber'12- This valve may Vbe of any suitableconstruction, but I have herein chosen to-employ for this purpose -a hollow shell which is guided on Va ,suitableV guide, herein a* plug Suitable provision is made for allowing the pressure within the inlet chamber 12 to be exerted on the valve 20 in such a manner as to tend to seatthe same, the plug 22 beingrherein provided for' this 4purpose with vent openings 23 and 24. Suitable means are 'provided for controlling this valve herein a piston 25 mounted in a suitable cylinder 26"and having a piston-rod 2.7 engaging the valve. This pistonrod is herein provided with a passage .28, which maintains in the space 29 at the `lefthand end oi' the cylinder'26 Vthe same pressure as existsl in Ythe` inlet chamber 12. Therefore, assuming 'that a pressure above atmosphericl pressure normallyexistswithin ythe inlet chamber 12, the 'inlet valve 20'will be seated-by the action of the pres-V sure acting,thereagainsqas well as against the left-hand end4 of the `piston 25. This may be Vassisted however, if desired, by

means oi' a 'spring 30 bearing against: the` piston 25, and tendingto keep the pistonrod-27 pressed against the valve 20, which in turn -is pressed against its seat. Y

)Vithin the cylinder 2G, there is provided a space Slat the right-hand side of the piston (Fig. 3), this spacecommunicating with the atmosphere through a vent-hole 32.

The diameter of the piston 25 Yand the ten-` sionof thespring 30 may be so proportioned that. they will hold the valve 2O seated against the maximum pressureV within the cylinder actmgagainst the end of the valveV through the port-V 21, tendingto raise the valve@ ssuming now Vthat the unloading valvejon the main inlet closes due to thefact thatthe` pressure inthe main receiver has reached ,the desired limitand that in consequence of the removal Vof the air in the inlet space 12 by the actionioitthe.piston 19, the

pressure in this vspace 'willfall-below nor-1. mal :as ftheinterlor of the valve 20 and thel space 29 at the leftV ofthe piston are Vin communication with the space 12,' the pressure in thesespaces will likewise fall. The

piston 19 in the cylinder 6, meanwhile, is traveling toward the left and compressing the air trapped withinv the cylinder up to a point where the reduced `pressure on the valve 2O and its piston 25 and the tension of thespring 30 is no longer sufficient to keep the valve seated. The valve will then rise, and instead of the air being discharged through-the regular discharge valve 17, it will simply flow back into the space 12 through the port 21, so that instead of compressing-the air up to the final terminal pressure, it will be compressed but a comparatively few pounds and returned to the space 12 to pass again into the cylinder on the suction stroke, this process being repeated as long as the unloading valve on the main inlet remains closed. In the meantime, no air is being discharged from the machine into the main receiver, andV as some air is bound to leak in around the unloading valve on the main inlet and from other sources of leakage, there will be an accumulation of air in the machine which will gradually raise the pressure in the inlet space 12. When this pressure rises above the point where the pressure within the interior of the valve 20 and in the space 29 is more than suiiicient to overcome the pressure in the main cylinder 6, acting on the end of the valve from the port 21,V the valve will be forced to its seat, and when this occurs the excess air will be discharged through the discharge valve 17.

It will be understood from the foregoing that the auxiliary valve acts automatically to prevent diminution of pressure in the connections between the high and low-pressure cylinders to a point below atmospheric pressure when the main unloading valve closes, or in other words, the valve acts automatically to place the high-pressure cylinder in communication with the connections between the cylinders when the pressure within said connections falls below normal. It will also be seen that when the valve is applied to any cylinder beyond the intake-cylinder, when the unloading valve on the main inlet opens, the first cylinder will begin to receive air, and will compress the same into the next succeeding cylinder; this will quickly build up the pressure in the passages between the two cylinders, and will thus furnish a motive force sufficient to close the auxiliary unloading valve.

'While I have herein shown and described one form of my invention for illustrative purposes, and have disclosed and discussed in detail the construction and arrangement incidental to one specific application thereof, it is to be understood that the invention is limited neither to the mere details or relative arrangement of parts, nor to its specific embodiment herein shown, but that extensive deviations from the illustrated form or embodiment of the invention may be made without departing from the principles thereof.

. Having thus described one embodiment of my invention, what I claim is 1. In a multi-stage elastic iiuid compressor, the combination of a plurality of compressor units, each having a cylinder and a piston, and one delivering to another, of an unloading valve for the inlet of one of said compressor units, an inlet valve for the succeeding compressor unit, the cylinder of said succeeding compressor unit having a port communicating with the connections etween the compressor units, a valve for said port normally held seated by the pressure within said connections, and means operated by atmospheric pressure to release the last-mentioned valve and allow the same to open under the influence of pressure in said cylinder when the pressure within said connections falls below normal.

2. In a multi-stage `elastic fluid compressor, the combination of a plurality of compressor units each having a cylinder and apiston, and one delivering to another, of an unloading valve for the inlet of one of said compressor units, an inlet valve for the succeeding compressor unit, the cylinder of said succeeding compressor unit having a port communicating with the connections between tlie compressor units, a valve for said port, yielding means normally tending nto scat the last-mentioned valve, and means operated by atmospheric pressure to act against said yielding means to release the last-mentioned valve and allow the same to open under the influence of pressure in said cylinder when the pressure within said connection falls below normal.

3. In a multi-stage elastic fluid compressor, the combination of a plurality of compressor units each having a cylinder and a piston, and one delivering to another, of an unloading valve for the inlet of one of said compressor units, an inlet valve for the succeeding compressor unit, the cylinder of said succeeding compressor unit having a port communicating with the connections between the compressor units, a valve for said port, yielding means cooperating with the pressure within said connections normally tending to seat the last-mentioned valve, and means operated by atmospheric pressure to act against said yielding means to release the last-mentioned valve and allow the same to open under the iniiucnce of pressure in said cylinder when the pressure within said connections falls below normal.

4. In a multi-stage elastic fluid compressor7 the combination of a plurality of compressor units each having a cylinder and a piston, and one delivering to another, of an unloadingvalve for the inlet of one of said compressor units, an inlet valve for the succeeding compressor unit, the cylinder of il munication between the other side of the said succeeding `compressor unit having a connections falls below normal.

5. In a iiiulti-stage elastic iiuid compressor, ythe combination of a` plurality of compressor units each having a cylinder and a piston, and one delivering to another', of an unloading valve for the inlet of one of said' compressor units7 an inlet valve .for the succeeding compressor unit, the cylinder of said succeeding compressor unit having a port communicating with the connection between the compressor units, a valve for said port, a piston for controlling the lastinentioned valve, a cylinder for said valveactuating piston communicating on one side of the latter with the atmosphere, and a piston-rod having a passage forming a com- Copies of this patent may be obtained for five cents each, by addressing rthe Commissioner of Patents,l

last-me1itioned cylinder Vand said connections.

6. lnv a multi-stage Velastic -luid Vcompresser, the combination of :a plurality of compressor units each having a cylinder anda piston, and one delivering to another,-

of an unloading valve for the inlet of one of said compressor units'7 an vinlet valve for the succeeding lcompressor unit, the cylinder ofsaid succeeding compressor unit having a port communicating with the connections between the compressor units, a hollow valve for said port, aguide for said valve having toirrod also guided by said guide'and having a passage forming a communication between the other side of the last-mentioned cylinder and said connections. Y. ln testimony whereof, I have signed my naine `to this specification7 in the presence of two subscribing.witnesses. .Y Y

Y FRED D. HOLDSWORTH. lVitnesses: v Y f v Trroiiiis B. BOOTH, EVERETT S. EMERY.

Washington, D. G. 

